Oxygen scavenging enhances exothermic behavior of aluminum-fueled energetic composites

Abstract

The theoretical heat of combustion for aluminum (Al) and copper oxide (CuO) under ideal conditions is roughly 4,100 kJ kg−1, but in practice only a fraction of this energy is available for application. Approaching the theoretical value requires innovative strategies for exploiting reaction kinetics. One strategy is to force Al to react CuO as opposed to oxygen from the environment and this approach was shown here to improve the measured heat of combustion significantly. This was achieved through tailoring the mixture using an additive with oxygen affinity prior to Al ignition. The additive is hafnium hydride (HfH2) and this study examines reaction kinetics for HfH2 0–60 mass% concentration range using simultaneous thermal-gravimetric analysis. Results reveal that 0–10 mass% HfH2 additive enhanced the heat of combustion of Al+CuO by 12 %. The observed enhancement is attributed to HfH2 creating oxidation competitions that directly influence the combustion performance of Al+CuO. The transition of this equilibrium-based observation to a non-equilibrium fast heating setup is also investigated using plate deformation tests. Exploding bridge wire heads initiated by a capacitive discharge unit are used to dent plates and the deformation energies are estimated to observe the effects of varying composites in a non-equilibrium setting. The presence of HfH2 showed improved deformation energies for Al+CuO in the 10 % mass HfH2 range. This work introduces a novel method of using a catalyst in thermite composites to enhance combustive behaviors through oxygen scavenging. Using the same concept as getter materials, the atmosphere is scavenged of free oxygen allowing for the fuel to react exclusively with the solid oxidizer.